In many communication networks, data is exchanged as a series of messages, commonly referred to as a communication sequence or flow. Each message in the flow is divided into one or more packets, which are typically sent from one network device to another. Packets are numbered so that they can be reassembled into messages once delivered to a receiving network device. To preserve data integrity, a sending network device checks the outgoing data for errors. A single network device can support thousands of flows. When an error is detected in a flow, the sending network device notifies software and stops transmitting further packets in that flow.
A common mechanism (or protocol) used for managing message flows is the InfiniBand™ standard (the specification of which is incorporated herein by reference). In accordance with this protocol, a transmitting device (a requester) sequentially transmits a flow of messages containing one or more packets to a receiving device (a responder). The responder receives the message packets in the flow, detects errors, and sequentially reports the status of each of the received packets back to the requester. Once the responder reports a remote error to the requester, the responder will not accept any more packets in that flow. Errors reported by the responder are called remote errors because they are detected remotely from the requester. Once the requester receives a report of a packet containing a remote error the error is reported to software in a completion code and any subsequent reports for the flow from the responder are ignored.
While preparing to transmit a flow to the responder, the requester may detect transmission errors. Transmission errors may be detected after packets earlier in the flow sequence have been sent to the responder. Conventionally, when the requester detects a transmission error in a packet, it is immediately reported to software so that the flow can be promptly terminated. InfiniBand™ specifies that the requester must immediately report all errors that it detects.